Metalized ceramic bodies can be obtained by metalizing either fired or unfired--or green--ceramic bodies. Metalizing the green ceramic ware has the advantage that firing is done only once and is used particularly in the production of multi-layer ceramic substrates.
One method of metalizing green ceramic ware and sintering the metalizing and the ceramic in common to produce a multi-layer ceramic substrate from ceramic sheets having a metallurgy pattern and/or metal-filled via holes is described, for example, in European Pat. No. 43 029. An electrically conductive paste, for example a molybdenum paste, is applied to and introduced into suitable embodied green sheets, for example comprising a mixture of 89% by weight of aluminum oxide, 11% of weight of a glass and a liquid vehicle. Then the green ceramic sheets and the molybdenum metalizing are fired or sintered in common (co-firing, simultaneous sintering).
In the method for producing multi-layer ceramic chip carrier modules known from European Pat. No. 50 903, the conductor paste, for example a tungsten or molybdenum paste, is once again applied to the ceramic green sheets and sintered in common with it at 900.degree.-1550.degree. C. The ceramic in this case may be aluminum oxide, beryllium oxide, steatite, mullite or barium titanate, for example.
In the method known from European Pat. No. 61 010 as well, a refractory metal layer is printed onto an unfired ceramic substrate. The metalizing layer contains the refractory metal molybdenum, tantalum or tungsten and optionally up to 5% by weight of a glass frit as an additional inorganic component and also contains an organic vehicle. The metalizing layer is sintered at the same time as the unfired substrate. The presence of a thin film of palladium catalytically influences the sintering of the metal. If the ceramic comprises aluminum oxide, the sintering is performed particularly at 1600.degree. C. in wet hydrogen.
European Patent Application No. 124 836 relates to non-oxide ceramic bodies, for instance of silicon nitride, provided with conductive coatings of molybdenum or tungsten silicide, which may optionally contain a nitride of a metal of column IVa of a periodic table (European convention), such as titanium nitride. The metalized ceramic bodies are produced by applying a metal molybdate or metal tungstate to the sintered ceramic, melting the molybdate or tungstate and sintering in a reducing atmosphere.
Circuit substrates of aluminum nitride ceramic, which for instance contains yttrium oxide to increase its thermal conductivity and to make it wettable, having electrically conductive films or layers are known from European Patent Application No. 153 737. The films are produced by firing of thick-film pastes applied to sintered aluminum nitride ceramic. A strong bond of the films is accomplished by using thick-film pastes containing copper oxide, lead or silicon, or by causing an oxide film to form on the ceramic.
To cause the densification temperature of the metal member to be closer to or identical with curing temperature of the substrate, it is possible--as proposed in European Patent Application No. 177 772--to add to the metal, which is typically in the form of a paste, a metal, a metal oxide, or an organometallic compound that is capable of decomposition into the metal or metal oxide. Sintering is done at 500.degree.-1800.degree. C. in the absence or presence of a reducing atmosphere.
German Patent Disclosure Document DE-OS No. 33 40 926 relates to substrate structures having conductor pathes comprising zirconium boride or tantalum boride, or comprising tungsten, molybdenum or tantalum. They are produced by screen printing the conductor pathes onto pre-shaped sheets, obtained by pressing powdered silicon carbide with a small quantity of beryllium oxide as a sintering aid, and then hot-pressing the product in argon, helium or nitrogen. Instead of the silicon carbide, silicon nitride or boron nitride may for instance be contained in the substrate structures.